> > Without this override, performance drops by around 15% on> > network throughput tests on this system.> > The question is, _why_ does network performance drop?>> Do you have a before/after pair of /proc/interrupts output> perhaps? Does the layout of IRQs change?>> The system is not SMP - so only something about UP-IOAPIC can> be helpful to performance here - or some unknown effect.

I presume it is IOAPIC (good) vs PIC (bad), for the patch that provoked this regression was one that causedthe MPS table to be disabled. (the problem with that patchwas that it was effective not just in ACPI mode, but in acpi=off mode)

The other un-answered question is why the system under testhas ACPI disabled in the BIOS when it did not ship thatway from the manufacturer.